Its Nobel Prize season. In Stockholm this week, Nobel officials will announce winners in the natural sciences and literature. Friday the Peace Prize will be announced in Oslo, Norway. First off this morning is the Nobel Prize in physiology or medicine. NPR health correspondent Rob Stein joins us in the studio. Good morning, Rob.

ROB STEIN, BYLINE: Good morning.

MARTIN: So who won?

STEIN: Well, the $1.1 million prize was split between John O'Keefe of University College in London and a husband-and-wife team, May-Britt Moser and Edvard Moser of the Norwegian University in Trondheim, Norway. They won for discovering what the Nobel committee calls our inner GPS system - how our brains figure out where we are and how we get from one place to another.

MARTIN: Those are very good questions. So how did they figure this out?

STEIN: Well, John O'Keefe, he started his work in the 1960s. And in 1971 he did a series of experiments in which he recorded signals from individual nerve cells in the brain of rats moving around a room in the laboratory. He discovered a type of nerve cell in an area of the brain called the hippocampus. What he showed is that some of these cells were always activated when a rat was in a certain place in the room while others were active when the animal was in a different place. So by studying the patterns of these activity of these cells, he showed that these cells were essentially creating mental maps of the environment that enabled them to know where they were positioned in the world, and they could store these maps in their brains.

MARTIN: OK. So that was what O'Keefe discovered. What about the Mosers?

STEIN: So the Mosers did work, like, three decades later. In 2005 this husband-and-wife team were mapping connections among the brain cells in the hippocampus in rats when they discovered another kind of nerve cell in the hippocampus they called grid cells. These cells activated in a unique pattern to generate a kind of set of coordinates that enabled the brain not only to find positions, but to move from one place to another. This enabled the brain to kind of map a route and figure out how to get from one place to another. The grid cells created, like, circuits that allow the brain to navigate a complicated movement through the environment.

MARTIN: OK. So what does this mean to us? Why is this so significant?

STEIN: Well, you know, this is - the Nobel Committee says this is something that philosophers and brain scientists had speculated about for really hundreds of years, and they provided crucial, new information about how the brain produced complex behavior. The committee says the discovery of the brain's GPS system really represented a kind of a paradigm shift in how our brain - how specialized cells in the brain work together to create complicated thinking abilities. And that opened up whole new areas of understanding how our brains work in creating things like memory and planning.

MARTIN: Are there any big-picture kind of implications for human health at large?

STEIN: Well, research that's been done since this work showed that humans have these cells, too - these place cells and these grid cells and that in fact people who suffer from Alzheimer's disease tend to lose these abilities, so it's one of the first things that go. You know, they get lost easily; they can't find their way around. So while there are no immediate implications for human health, they think that one day, it could lead to things that could help, you know, people.